The sensitivity of a bone scan for diagnosing osteomyelitis is quite high, so a negative bone scan effectively rules out osteomyelitis. It is also relatively specific in the setting of otherwise normal bone, but the specificity drops markedly in the setting of trauma (as in this case) or hardware since all of these will induce osteoblastic activity and increased radiotracer uptake.

Dual isotope imaging with In-111 WBCs and Tc99m sulfur colloid is helpful in this scenario given its high specificity for infection. Both sulfur colloid and WBCs accumulate in the bone marrow, but only WBCs accumulate in sites of infection. With osteomyelitis, WBCs uptake is increased but sulfur colloid uptake is suppressed (as in this case), a situation which is termed incongruent. The incongruence can be either from intensity (SBC uptake >> sulfur colloid) or spacial (WBC uptake location different than sulfur colloid).